When soft contact lenses are worn, the lens surface tends to be getting dry and be deposited with pollen and pollutant substances that may cause allergic symptoms such as itchiness, inflammatory hyperemia and the like. Accordingly, there has been long demanded a composition for users of soft contact lenses, which contains an anti-inflammatory component, an antihistamine component or an anti-hyperemic component.
For the anti-inflammatory, antihistamine or anti-hyperemic component, there are known basic compounds containing a secondary amino group and/or a tertiary amino group. These basic chemical substances have high affinity for soft contact lenses, so that when used as a composition for users of soft contact lens, they have the possibility of being adsorbed on the lens surface and accumulated inside the lens as time passes, thus giving an adverse influence on the physical properties and the usability during wear of the lenses and also on the side effect thereof in some cases. In order to allow adaptation for the use of soft contact lenses, it is essential to suppress the basic chemical substance from being adsorbed on the lens.
Several methods of suppressing adsorption of chemical substances on a soft contact lens have been hitherto proposed including a method of suppressing adsorption of lipid soluble vitamins with a polymeric compound and a nonionic surface active agent (see Patent Document 1: Japanese Patent Laid-Open No. 2001-158734) and a method of suppressing adsorption of dipotassium glycyrrhizinate with an amino acid or the like (see Patent Document 2: Japanese Patent Laid-Open No. 2001-2563). However, ophthalmic compositions for suppressing adsorption, on soft contact lenses, of such a basic chemical substance as set out above have never been developed yet. Although there are known a method of suppressing adsorption of chlorpheniramine maleate on a container while controlling a pH of the composition to 5 to 6 (see Patent Document 3: Japanese Patent Laid-Open No. 2002-249445) and a method of suppressing adsorption on a container by formulating cyclodextrin (see Patent Document 4: Japanese Patent Laid-Open No. 2004-359679), no method of suppressing adsorption on soft contact lenses has been known. It is to be noted that prior art literatures related to the present invention are mentioned below.
Patent Document 1:    Japanese Patent Laid-Open No. 2001-158734
Patent Document 2:    Japanese Patent Laid-Open No. 2001-2563
Patent Document 3:    Japanese Patent Laid-Open No. 2002-249445
Patent Document 4:    Japanese Patent Laid-Open No. 2004-359679
Patent Document 5:    Japanese Patent Laid-Open No. 2002-322048
Patent Document 6:    Japanese Patent Laid-Open No. 2001-122774
Patent Document 7:    Japanese Patent Laid-Open No. 2004-2364
Patent Document 8:    Japanese Patent Laid-Open No. 2003-252800
Patent Document 9:    Japanese Patent Laid-Open No. 2001-158750
Patent Document 10:    Japanese Patent Laid-Open No. 2003-2837